Systems and methods for reducing collisions after traffic indication map paging

ABSTRACT

Systems, methods, and devices for reducing collisions in a wireless communications network are described herein. In some aspects, a processor is configured to decrementing a value of a counter if a channel of a wireless communications network is idle for at least an extended slot time. The processor may be further configured to generate a polling request and allow the transmission of the polling request to an access point over the wireless communications network when the value of the counter reaches a threshold value.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. §119(e) to U.S.Provisional Patent Application No. 61/595,480, filed on Feb. 6, 2012,and U.S. Provisional Patent Application No. 61/758,000, filed on Jan.29, 2013, entitled “SYSTEMS AND METHODS FOR REDUCING COLLISIONS AFTERTRAFFIC INDICATION MAP PAGING”, the entire contents of which disclosureis herewith incorporated by reference.

BACKGROUND

1. Field

The present application relates generally to wireless communications,and more specifically to systems, methods, and devices for performingcollision avoidance in a wireless communication network.

2. Background

In many telecommunication systems, communications networks are used toexchange messages among several interacting spatially-separated devices.Networks may be classified according to geographic scope, which couldbe, for example, a metropolitan area, a local area, or a personal area.Such networks would be designated respectively as a wide area network(WAN), metropolitan area network (MAN), local area network (LAN),wireless local area network (WLAN), or personal area network (PAN).Networks also differ according to the switching/routing technique usedto interconnect the various network nodes and devices (e.g., circuitswitching vs. packet switching), the type of physical media employed fortransmission (e.g., wired vs. wireless), and the set of communicationprotocols used (e.g., Internet protocol suite, SONET (SynchronousOptical Networking), Ethernet, etc.).

Wireless networks are often preferred when the network elements aremobile and thus have dynamic connectivity needs, or if the networkarchitecture is formed in an ad hoc, rather than fixed, topology.Wireless networks employ intangible physical media in an unguidedpropagation mode using electromagnetic waves in the radio, microwave,infra-red, optical, etc. frequency bands. Wireless networksadvantageously facilitate user mobility and rapid field deployment whencompared to fixed wired networks.

The devices in a wireless network may transmit/receive informationbetween each other. Further, devices that are not activelytransmitting/receiving information in the wireless network may enter adoze state, to conserve power, where the devices do not activelytransmit/receive information in the doze state. These devices mayfurther utilize paging messages to determine when to wake up from a dozestate and enter an awake state in order to transmit/receive data. Thus,improved systems, methods, and devices for reducing collisions aredesired.

SUMMARY

The systems, methods, and devices of the invention each have severalaspects, no single one of which is solely responsible for its desirableattributes. Without limiting the scope of this invention as expressed bythe claims which follow, some features will now be discussed briefly.After considering this discussion, and particularly after reading thesection entitled “Detailed Description” one will understand how thefeatures of this invention provide advantages that include improvedpaging for devices in a wireless network.

One aspect of this disclosure provides a wireless communications device.The wireless communications device comprises a memory configured tostore a value of a counter. The wireless communications device furthercomprises a processor coupled to the memory. The processor is configuredto decrement the value of the counter if a channel of a wirelesscommunications network is idle for at least an extended slot time. Astarting value of the counter is based on a position of an indexcorresponding to the wireless communications device in an informationelement. The processor is further configured to generate a pollingrequest. The polling request is transmitted to an access point over thewireless communications network when the value of the counter reaches athreshold value.

Another aspect of this disclosure provides a method for reducingcollisions in a wireless communications network. The method comprisesdecrementing a value of a counter if a channel of a wirelesscommunications network is idle for at least an extended slot time. Astarting value of the counter is based on a position of an indexcorresponding to a wireless communications device in an informationelement. The method further comprises generating a polling request. Themethod further comprises transmitting the polling request to an accesspoint over the wireless communications network when the value of thecounter reaches a threshold value.

Another aspect of this disclosure provides an apparatus configured toreduce collisions in a wireless communications network. The apparatuscomprises means for decrementing a value of a counter if a channel of awireless communications network is idle for at least an extended slottime. A starting value of the counter is based on a position of an indexcorresponding to a wireless communications device in an informationelement. The apparatus further comprises means for generating a pollingrequest. The apparatus further comprises means for transmitting thepolling request to an access point over the wireless communicationsnetwork when the value of the counter reaches a threshold value.

Another aspect of this disclosure provides a non-transitory computerreadable medium comprising instructions or code that, when executed,causes an apparatus to decrement a value of a counter if a channel of awireless communications network is idle for at least an extended slottime. A starting value of the counter is based on a position of an indexcorresponding to a wireless communications device in an informationelement. The medium further comprises code that, when executed, causesthe apparatus to generate a polling request. The medium furthercomprises code that, when executed, causes the apparatus to transmit thepolling request to an access point over the wireless communicationsnetwork when the value of the counter reaches a threshold value.

Another aspect of this disclosure provides a wireless communicationsdevice. The wireless communications device comprises a receiverconfigured to detect messages transmitted on a channel of a wirelesscommunications network. The wireless communications device furthercomprises a processor coupled to the receiver. The processor isconfigured to generate a polling request. The processor is furtherconfigured to determine an adaptive enhanced inter-frame space (AEIFS)each time the wireless communications device detects another messagetransmitted on the channel of the wireless communications network inwhich the wireless communications device communicates. An initialduration of the AEIFS is based on a position of the wirelesscommunication device in an information element. The polling request istransmitted to an access point over the wireless communications networkafter a time based on a duration of the AEIFS and when the channel ofthe wireless communications network is open.

Another aspect of this disclosure provides a method for reducingcollisions in a wireless communications network. The method comprisesgenerating a polling request. The method further comprises determiningan adaptive enhanced inter-frame space (AEIFS) each time a wirelesscommunications device detects another message transmitted on a channelof a wireless communications network in which the wirelesscommunications device communicates. An initial duration of the AEIFS isbased on a position of the wireless communication device in aninformation element. The method further comprises transmitting thepolling request to an access point over the wireless communicationsnetwork after a time based on a duration of the AEIFS and when thechannel of the wireless communications network is open.

Another aspect of this disclosure provides an apparatus configured toreduce collisions in a wireless communications network. The apparatuscomprises means for generating a polling request. The apparatus furthercomprises means for determining an adaptive enhanced inter-frame space(AEIFS) each time a wireless communications device detects anothermessage transmitted on a channel of a wireless communications network inwhich the wireless communications device communicates. An initialduration of the AEIFS is based on a position of the wirelesscommunication device in an information element. The apparatus furthercomprises means for transmitting the polling request to an access pointover the wireless communications network after a time based on aduration of the AEIFS and when the channel of the wirelesscommunications network is open.

Another aspect of this disclosure provides a non-transitory computerreadable medium comprising instructions or code that, when executed,causes an apparatus to generate a polling request. The medium furthercomprises code that, when executed, causes an apparatus to determine anadaptive enhanced inter-frame space (AEIFS) each time a wirelesscommunications device detects another message transmitted on a channelof a wireless communications network in which the wirelesscommunications device communicates. An initial duration of the AEIFS isbased on a position of the wireless communication device in aninformation element. The medium further comprises code that, whenexecuted, causes an apparatus to transmit the polling request to anaccess point over the wireless communications network after a time basedon a duration of the AEIFS and when the channel of the wirelesscommunications network is open.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an exemplary wireless communication system in which aspectsof the present disclosure may be employed.

FIG. 2 shows a functional block diagram of an exemplary wireless devicethat may be employed within the wireless communication system of FIG. 1.

FIG. 3 illustrates a plurality of partitioned paging messagestransmitted by an access point to wireless stations in the wirelesscommunication system of FIG. 1.

FIG. 4 illustrates an exemplary polling request mechanism.

FIG. 5A illustrates another polling request mechanism.

FIG. 5B illustrates another exemplary polling request mechanism.

FIG. 6 illustrates another exemplary polling request mechanism.

FIG. 7 is a flowchart of a process for reducing collisions in thewireless communication system of FIG. 1.

FIG. 8 is a functional block diagram of an exemplary wireless devicethat may be employed within the wireless communication system of FIG. 1.

FIG. 9 is another flowchart of a process for reducing collisions in thewireless communication system of FIG. 1.

FIG. 10 is another functional block diagram of an exemplary wirelessdevice that may be employed within the wireless communication system ofFIG. 1.

DETAILED DESCRIPTION

Various aspects of the novel systems, apparatuses, and methods aredescribed more fully hereinafter with reference to the accompanyingdrawings. This disclosure may, however, be embodied in many differentforms and should not be construed as limited to any specific structureor function presented throughout this disclosure. Rather, these aspectsare provided so that this disclosure will be thorough and complete, andwill fully convey the scope of the disclosure to those skilled in theart. Based on the teachings herein one skilled in the art shouldappreciate that the scope of the disclosure is intended to cover anyaspect of the novel systems, apparatuses, and methods disclosed herein,whether implemented independently of, or combined with, any other aspectof the invention. For example, an apparatus may be implemented or amethod may be practiced using any number of the aspects set forthherein. In addition, the scope of the invention is intended to coversuch an apparatus or method which is practiced using other structure,functionality, or structure and functionality in addition to or otherthan the various aspects of the invention set forth herein. It should beunderstood that any aspect disclosed herein may be embodied by one ormore elements of a claim.

Although particular aspects are described herein, many variations andpermutations of these aspects fall within the scope of the disclosure.Although some benefits and advantages of the preferred aspects arementioned, the scope of the disclosure is not intended to be limited toparticular benefits, uses, or objectives. Rather, aspects of thedisclosure are intended to be broadly applicable to different wirelesstechnologies, system configurations, networks, and transmissionprotocols, some of which are illustrated by way of example in thefigures and in the following description of the preferred aspects. Thedetailed description and drawings are merely illustrative of thedisclosure rather than limiting, the scope of the disclosure beingdefined by the appended claims and equivalents thereof.

Popular wireless network technologies may include various types ofwireless local area networks (WLANs). A WLAN may be used to interconnectnearby devices together, employing widely used networking protocols. Thevarious aspects described herein may apply to any communicationstandard, such as a wireless protocol.

In some aspects, wireless signals in a sub-gigahertz band may betransmitted according to the 802.11ah protocol using orthogonalfrequency-division multiplexing (OFDM), direct-sequence spread spectrum(DSSS) communications, a combination of OFDM and DSSS communications, orother schemes. Implementations of the 802.11ah protocol may be used forsensors, metering, and smart grid networks. Advantageously, aspects ofcertain devices implementing the 802.11ah protocol may consume lesspower than devices implementing other wireless protocols, and/or may beused to transmit wireless signals across a relatively long range, forexample about one kilometer or longer.

In some implementations, a WLAN includes various devices which are thecomponents that access the wireless network. For example, there may betwo types of devices: access points (“APs”) and clients (also referredto as stations, or “STAs”). In general, an AP may serve as a hub or basestation for the WLAN and an STA serves as a user of the WLAN. Forexample, an STA may be a laptop computer, a personal digital assistant(PDA), a mobile phone, etc. In an example, an STA connects to an AP viaa WiFi (e.g., IEEE 802.11 protocol such as 802.11ah) compliant wirelesslink to obtain general connectivity to the Internet or to other widearea networks. In some implementations an STA may also be used as an AP.

An access point (“AP”) may also comprise, be implemented as, or known asa NodeB, Radio Network Controller (“RNC”), eNodeB, Base StationController (“BSC”), Base Transceiver Station (“BTS”), Base Station(“BS”), Transceiver Function (“TF”), Radio Router, Radio Transceiver, orsome other terminology.

A station “STA” may also comprise, be implemented as, or known as anaccess terminal (“AT”), a subscriber station, a subscriber unit, amobile station, a remote station, a remote terminal, a user terminal, auser agent, a user device, user equipment, or some other terminology. Insome implementations an access terminal may comprise a cellulartelephone, a cordless telephone, a Session Initiation Protocol (“SIP”)phone, a wireless local loop (“WLL”) station, a personal digitalassistant (“PDA”), a handheld device having wireless connectioncapability, or some other suitable processing device connected to awireless modem. Accordingly, one or more aspects taught herein may beincorporated into a phone (e.g., a cellular phone or smartphone), acomputer (e.g., a laptop), a portable communication device, a headset, aportable computing device (e.g., a personal data assistant), anentertainment device (e.g., a music or video device, or a satelliteradio), a gaming device or system, a global positioning system device,or any other suitable device that is configured to communicate via awireless medium.

As discussed above, certain of the devices described herein mayimplement the 802.11ah standard, for example. Such devices, whether usedas an STA or AP or other device, may be used for smart metering or in asmart grid network. Such devices may provide sensor applications or beused in home automation. The devices may instead or in addition be usedin a healthcare context, for example for personal healthcare. They mayalso be used for surveillance, to enable extended-range Internetconnectivity (e.g. for use with hotspots), or to implementmachine-to-machine communications.

FIG. 1 shows an exemplary wireless communication system 100 in whichaspects of the present disclosure may be employed. The wirelesscommunication system 100 may operate pursuant to a wireless standard,for example the 802.11ah standard. The wireless communication system 100may include an AP 104, which communicates with STAs 106.

A variety of processes and methods may be used for transmissions in thewireless communication system 100 between the AP 104 and the STAs 106.For example, signals may be sent and received between the AP 104 and theSTAs 106 in accordance with OFDM/OFDMA techniques. If this is the case,the wireless communication system 100 may be referred to as anOFDM/OFDMA system. Alternatively, signals may be sent and receivedbetween the AP 104 and the STAs 106 in accordance with CDMA techniques.If this is the case, the wireless communication system 100 may bereferred to as a CDMA system.

A communication link that facilitates transmission from the AP 104 toone or more of the STAs 106 may be referred to as a downlink (DL) 108,and a communication link that facilitates transmission from one or moreof the STAs 106 to the AP 104 may be referred to as an uplink (UL) 110.Alternatively, a downlink 108 may be referred to as a forward link or aforward channel, and an uplink 110 may be referred to as a reverse linkor a reverse channel.

The AP 104 may act as a base station and provide wireless communicationcoverage in a basic service area (BSA) 102. The AP 104 along with theSTAs 106 associated with the AP 104 and that use the AP 104 forcommunication may be referred to as a basic service set (BSS). It shouldbe noted that the wireless communication system 100 may not have acentral AP 104, but rather may function as a peer-to-peer networkbetween the STAs 106. Accordingly, the functions of the AP 104 describedherein may alternatively be performed by one or more of the STAs 106.

The AP 104 may transmit a beacon signal (or simply a “beacon”), via acommunication link such as the downlink 108, to other nodes STAs 106 ofthe system 100, which may help the other nodes STAs 106 to synchronizetheir timing with the AP 104, or which may provide other information orfunctionality. Such beacons may be transmitted periodically. In oneaspect, the period between successive transmissions may be referred toas a superframe. Transmission of a beacon may be divided into a numberof groups or intervals. In one aspect, the beacon may include, but isnot limited to, such information as timestamp information to set acommon clock, a peer-to-peer network identifier, a device identifier,capability information, a superframe duration, transmission directioninformation, reception direction information, a neighbor list, and/or anextended neighbor list, some of which are described in additional detailbelow. Thus, a beacon may include information both common (e.g. shared)amongst several devices, and information specific to a given device.

In some aspects, a STA 106 may be required to associate with the AP 104in order to send communications to and/or receive communications fromthe AP 104. In one aspect, information for associating is included in abeacon broadcast by the AP 104. To receive such a beacon, the STA 106may, for example, perform a broad coverage search over a coverageregion. A search may also be performed by the STA 106 by sweeping acoverage region in a lighthouse fashion, for example. After receivingthe information for associating, the STA 106 may transmit a referencesignal, such as an association probe or request, to the AP 104. In someaspects, the AP 104 may use backhaul services, for example, tocommunicate with a larger network, such as the Internet or a publicswitched telephone network (PSTN).

FIG. 2 shows an exemplary functional block diagram of a wireless device202 that may be employed within the wireless communication system 100 ofFIG. 1. The wireless device 202 is an example of a device that may beconfigured to implement the various methods described herein. Forexample, the wireless device 202 may comprise the AP 104 or one of theSTAs 106.

The wireless device 202 may include a processor 204 which controlsoperation of the wireless device 202. The processor 204 may also bereferred to as a central processing unit (CPU). Memory 206, which mayinclude both read-only memory (ROM) and random access memory (RAM), mayprovide instructions and data to the processor 204. A portion of thememory 206 may also include non-volatile random access memory (NVRAM).The processor 204 typically performs logical and arithmetic operationsbased on program instructions stored within the memory 206. Theinstructions in the memory 206 may be executable to implement themethods described herein.

The processor 204 may comprise or be a component of a processing systemimplemented with one or more processors. The one or more processors maybe implemented with any combination of general-purpose microprocessors,microcontrollers, digital signal processors (DSPs), field programmablegate array (FPGAs), programmable logic devices (PLDs), controllers,state machines, gated logic, discrete hardware components, dedicatedhardware finite state machines, or any other suitable entities that canperform calculations or other manipulations of information.

The processing system may also include machine-readable media forstoring software. Software shall be construed broadly to mean any typeof instructions, whether referred to as software, firmware, middleware,microcode, hardware description language, or otherwise. Instructions mayinclude code (e.g., in source code format, binary code format,executable code format, or any other suitable format of code). Theinstructions, when executed by the one or more processors, cause theprocessing system to perform the various functions described herein.

The wireless device 202 may also include a housing 208 that may includea transmitter 210 and/or a receiver 212 to allow transmission andreception of data between the wireless device 202 and a remote location.The transmitter 210 and receiver 212 may be combined into a transceiver214. An antenna 216 may be attached to the housing 208 and electricallycoupled to the transceiver 214. The wireless device 202 may also include(not shown) multiple transmitters, multiple receivers, multipletransceivers, and/or multiple antennas.

The transmitter 210 may be configured to wirelessly transmit messages,which may be referred to as “paging messages” that are configured toindicate to wireless devices whether or not the wireless devices need towake up from a doze state and enter an awake state as discussed below.For example, the transmitter 210 may be configured to transmit pagingmessages generated by the processor 204, discussed above. When thewireless device 202 is implemented or used as a STA 106, the processor204 may be configured to process paging messages. When the wirelessdevice 202 is implemented or used as an AP 104, the processor 204 mayalso be configured to generate paging messages.

The receiver 212 may be configured to wirelessly receive pagingmessages.

The wireless device 202 may also include a signal detector 218 that maybe used in an effort to detect and quantify the level of signalsreceived by the transceiver 214. The signal detector 218 may detect suchsignals as total energy, energy per subcarrier per symbol, powerspectral density and other signals. The wireless device 202 may alsoinclude a digital signal processor (DSP) 220 for use in processingsignals. The DSP 220 may be configured to generate a packet fortransmission. In some aspects, the packet may comprise a physical layerdata unit (PPDU).

The wireless device 202 may further comprise a user interface 222 insome aspects. The user interface 222 may comprise a keypad, amicrophone, a speaker, and/or a display. The user interface 222 mayinclude any element or component that conveys information to a user ofthe wireless device 202 and/or receives input from the user.

The various components of the wireless device 202 may be coupledtogether by a bus system 226. The bus system 226 may include a data bus,for example, as well as a power bus, a control signal bus, and a statussignal bus in addition to the data bus. Those of skill in the art willappreciate the components of the wireless device 202 may be coupledtogether or accept or provide inputs to each other using some othermechanism.

Although a number of separate components are illustrated in FIG. 2,those of skill in the art will recognize that one or more of thecomponents may be combined or commonly implemented. For example, theprocessor 204 may be used to implement not only the functionalitydescribed above with respect to the processor 204, but also to implementthe functionality described above with respect to the signal detector218 and/or the DSP 220. Further, each of the components illustrated inFIG. 2 may be implemented using a plurality of separate elements.

The wireless device 202 may comprise an AP 104 or an STA 106, and may beused to transmit and/or receive communications including pagingmessages. That is, either AP 104 or STA 106 may serve as transmitter orreceiver devices of paging messages. Certain aspects contemplate signaldetector 218 being used by software running on memory 206 and processor204 to detect the presence of a transmitter or receiver.

The STA 106 may have a plurality of operational modes. For example, theSTA 106 may have a first operational mode referred to as an active mode.In the active mode, the STA 106 may always be in an “awake” state andactively transmit/receive data with the AP 104. Further, the STA 106 mayhave a second operational mode referred to as a power save mode. In thepower save mode, the STA 106 may be in the “awake” state or a “doze” or“sleep” state where the STA 106 does not actively transmit/receive datawith the AP 104. For example, the receiver 212 and possibly DSP 220 andsignal detector 218 of the STA 106 may operate using reduced powerconsumption in the doze state. Further, in the power save mode, the STA106 may occasionally enter the awake state to listen to messages fromthe AP 104 (e.g., paging messages) that indicate to the STA 106 whetheror not the STA 106 needs to “wake up” (e.g., enter the awake state) at acertain time so as to be able to transmit/receive data with the AP 104.

Accordingly, in certain wireless communication systems 100, the AP 104may transmit paging messages to a plurality of STAs 106 in a power savemode in the same network as the AP 104, indicating whether or not thereis data buffered at the AP 104 for the STAs 106. The STAs 106 may alsouse this information to determine whether they need to be in an awakestate or a doze state. For example, if an STA 106 determines it is notbeing paged, it may enter a doze state. Alternatively, if the STA 106determines it may be paged, the STA 106 may enter an awake state for acertain period of time to receive the page and further determine when tobe in an awake state based on the page. Further, the STA 106 may stay inthe awake state for a certain period of time after receiving the page.In another example, the STA 106 may be configured to function in otherways when being paged or not being paged that are consistent with thisdisclosure.

In some aspects, paging messages may comprise a bitmap (not shown inthis figure), such as a traffic identification map (TIM). In certainsuch aspects, the bitmap may comprise a number of bits. These pagingmessages may be sent from the AP 104 to STAs 106 in a beacon or a TIMframe. Each bit in the bitmap may correspond to a particular STA 106 ofa plurality of STAs 106, and the value of each bit (e.g., 0 or 1) mayindicate the state the corresponding STA 106 should be in (e.g., dozestate or awake state). Accordingly, the size of the bitmap may bedirectly proportional to the number of STAs 106 in the wirelesscommunications system 100. Therefore, a large number of STAs 106 in thewireless communications system 100 may result in a large bitmap.

FIG. 3 illustrates a plurality of partitioned paging messages 302transmitted by the AP 104 to STAs 106 in the wireless communicationsystem 100 of FIG. 1. As shown, time increases horizontally across thepage over the time axis 304. As shown, the AP 104 is configured totransmit a plurality of paging messages 302. The paging messages 302 maybe sent in a TIM frame, a beacon, or using some other appropriatesignaling. The STAs 106 may be configured to listen to one or more ofthe paging messages 302. Following the one or more paging messages 302,the STAs 106 may be configured to transmit requests to the AP 104 andreceive a response from the AP 104.

The paging process may result in a high number of STAs 106 receiving theone or more paging messages 302. For example, a high number of STAs 106in the same TIM may receive the one or more paging messages 302, whichmay lead to one or more STAs 106 contending to transmit requests to theAP 104 on the medium after the TIM. Accordingly, collisions resulting incorrupted data received by the AP 104 may occur in situations in whichat least two STAs 106 attempt to transmit requests to the AP 104 at ornearly at a same time.

FIG. 4 illustrates a polling request mechanism 400. The polling requestmechanism 400 shown may be used by the AP 104 and the STAs 106 in thewireless communication system 100 of FIG. 1. As shown, time increaseshorizontally across the page from slot time 424 to slot time 440.

In general, after the transmission of a paging message, such as TIM 410,a time interval is reserved for the paged STAs 106. The reservation maybe achieved by transmitting a message (e.g., a paging message, anadditional message, etc.) to cause non-paged STAs to defer access to themedium for the duration of the reserved period. In some implementations,the deferred access can be achieved by setting a duration field value ofthe PPDU of a reserving frame (e.g., the paging message, the additionalmessage, etc.), which prompts the non-paged STAs to set their networkallocation vector (NAV). The PPDU of the reserving frame may carry aninformation element (e.g., the bitmap described above). In otherimplementations, the deferred access can be achieved by sending anadditional frame preceding or following the paging frame, where theadditional frame indicates the duration of the reserved period.

During the reserved time interval, the paged STAs 106 can send requeststo the AP 104 (e.g., Power Saving polls (PS-POLL) requests 412, 416, and420) and receive a response from the AP 104 (e.g., response 414, 418,and 422). Multiple paged STAs 106 can contend during the reserved timeinterval in accordance with various methods, as described herein. Insome embodiments, STAs 106 that have not been paged cannot contendduring the reserved time interval. Once the reserved time interval isover, STAs 106 can start contending to send the requests to the AP 104.In an embodiment, the AP 104 may determine the duration of the reservedtime interval. The reserved time interval should be sufficient for allthe paged STAs 106 to send requests to the AP 104 and receive a responsefrom the AP 104. By way of example, and not limitation, the duration ofthe reserved time interval may be a function of the number of paged STAs106.

The polling request mechanism 400 illustrates an embodiment in whichSTAs 402, 404, and 406 can transmit requests, like PS-POLLs 412, 416,and 420, to AP 408 in such a way so as to avoid collisions. STAs 402,404, and 406 may be similar to STAs 106 as described herein. In someembodiments, the STAs 402, 404, and 406 may transmit requests to the AP408 in a certain order. AP 408 may be similar to AP 104 as describedherein. The paging message, such as TIM 410, may implicitly orexplicitly define an ordering for the STAs 402, 404, and 406. Forexample if the TIM 410 bitmap indicates that both STA 402 and STA 404are paged, then the TIM 410 bitmap also implicitly or explicitlyindicates whether STA 402 is before or after STA 404. In an example, theorder could be determined by the order in which the paged STAs appear inthe bitmap representation. Consider a bitmap {0, 1, 0, 0, 1, 1}, wherethe STA associated with the bit in position 2 is assumed to be beforethe STA associated with the bit in position 5. In some implementations,the compressed bitmap may be expressed as list of STA identifiers. Inthis case the sequence in which the STA identifiers appear in the listmay determine the order. Consider the list {13, 25, 5, 22}, where theSTA associated with identifier “13” is assumed to come before STAidentified by “5.” In another aspect, the order may be derived from thevalue of the STA identifier irrespective of the message representation.

In some implementations, the position of the STA 402, 404, or 406 withinthe TIM 410 bitmap sequence may be a function of the position of the STA402, 404, or 406 as described above. The order may further be dependenton other indications, the indications being either included in thepaging message or assumed to be known at the STAs 402, 404, and/or 406.For example, the indication may include the Timing SynchronizationFunction (TSF) within the paging message (e.g. TIM 410). In such animplementation, the first STA may be the one whose identifier is set to“1” and has a position within the TIM 410 bitmap sequence which is firstin the order after the position associated with the 12 least significantbits (LSBs) of the TSF. Many other functions incorporating variousindications can be included to achieve a similar result as that based onthe TSF. One beneficial result of including the TSF in the computationof the order is that the order may be changed at each transmission,provided that the portion of the used TSF is different at eachtransmission.

In some implementations, the sender of the paging message may determinethe order of the paged STAs according to any criteria including theusage of the ordering information. For example the sender, AP 408, mayorder the STAs 402, 404, and 406 based on their QoS requirements, powersaving requirements, or other performance parameters. It may bedesirable in some implementation for the sender of the paging message toinclude in the message an explicit indication of the order. Thisexplicit indication of the order may not be based on the TIM 410 bitmap,but rather on other factors as described herein.

For illustrative purposes only, and not meant to be limiting, FIG. 4depicts an order of STA 402, STA 404, and then STA 406. While STA 402may be the first STA to transmit a request to the AP 408, the STA 402may not do so immediately after the TIM 410. Each of STAs 402, 404, and406 may be configured to use a carrier sense multiple access withcollision avoidance (CSMA/CA) based medium access procedure, such as thedistributed coordination function (DCF) or the enhanced distributedchannel access (EDCA) as defined in the IEEE 802.11 standard. In such amedium access mechanism, a STA 402, 404, or 406 that wants to access themedium for the transmission of a frame initializes a back-off counter.The back-off counter may be initialized with a random number chosen inan appropriate interval. For example, an appropriate interval may be avalue between 0 and a duration of a contention window (CW). The back-offcounter may be decremented while the transmission medium (e.g. channel)is idle—in other words, no activity is detected on the transmissionmedium. The transmission medium may be considered to be idle if noactivity is detected for a distributed inter-frame space (DIFS) or anarbitration inter-frame space (AIFS) interval. After the medium has beenidle for a DIFS or AIFS interval of time, the back-off counter may bedecremented by one unit per each additional consecutive idle interval ofa duration equal to a slot time. When activity is detected on themedium, the back-off countdown may be frozen and restarted when themedium becomes idle again, as described herein. The STAs 402, 404, and406 may transmit a packet on the medium when the back-off counterreaches zero or any other integer that represents a lowest value of thecounter. In some implementations the DIFS interval may be defined as

DIFS=SIFS+(2*slot time)  (1)

where SIFS is a short inter-frame space. The AIFS interval may bedefined as

AIFS=SIFS+(n*slot time)  (2)

where n is greater than or equal to 2.

Each of STAs 402, 404, and 406 may be configured to use a deterministicback-off value to initialize a back-off counter, where an initial valueof the back-off counter may be based on the order of the paged STAs 402,404, and 406. For example, an initial value of the back-off counter forSTA 402 may be 1, an initial value of the back-off counter for STA 404may be 2, and an initial value of the back-off counter for STA 406 maybe 3. In this way, an initial value of the back-off counter may bedifferent for each STA 402, 404, and 406 so as to allow each STA 402,404, and 406 to access the medium in different time instants.

In some implementations, the back-off counter for each STA 402, 404, and406 may decrement the back-off value when the channel over which theSTAs 402, 404, and 406 communicate with the AP 408 is idle for theduration of a slot time 424, 426, 428, 430, 432, 434, 436, 438, and 440.As an example, a regular slot time may be a slot time defined in theIEEE 802.11 standard or a similar CSMA/CA protocol. The STAs 402, 404,and/or 406 may be configured to transmit a PS-POLL request 412, 416,and/or 420 when their respective back-off value reaches zero or anyother integer that represents a lowest value of the counter.

In some implementations, the paged STAs 402, 404, and/or 406 may performthe back-off procedure by using a DIFS, an AIFS, and a slot time thatare defined differently than the definitions found in the IEEE 802.11standard. In an embodiment, slot times 424, 426, 428, 430, 432, 434,436, 438, and 440 may be defined as extended slot times (hereinafterreferred to as “slot times”). Extended slot times may be at least aslong in duration as the time it takes for a STA 402, 404, or 406 totransmit a PS-POLL request 412, 416, or 420 and for the STA 402, 404, or406 to receive a beginning of a response 414, 418, or 422. For example,an extended slot time may be the sum of the time it takes for a STA 402,404, or 406 to transmit a PS-POLL request 412, 416, or 420, the SIFStime, and the clear channel assessment (CCA) time. In other words, theextended slot may be defined as

extended slot time=PS-POLL time+SIFS+CCA time  (3)

As an example, the extended slot time may be a multiple of a regularslot time, where the regular slot time is defined by the IEEE 802.11standard. For example,

$\begin{matrix}{\frac{{extended}\mspace{14mu} {slot}\mspace{14mu} {time}}{{regular}\mspace{14mu} {slot}\mspace{14mu} {time}} = K} & (4)\end{matrix}$

where K is an integer. In an embodiment, the DIFS or AIFS intervalduration used by the paged STAs 402, 404, and/or 406 may be the same ornearly the same as the duration as defined by the IEEE 802.11 standard.For example, the DIFS or AIFS interval duration used by the paged STAs402, 404, and/or 406 may be defined as in Equations (1) and (2) above.In another embodiment, the DIFS or AIFS interval duration used by thepaged STAs 402, 404, and/or 406 may be equal to zero. In this case, theback-off counter may be decremented by one unit per each consecutiveidle interval of a duration equal to an extended slot time, withoutwaiting for a DIFS or AIFS interval. In another embodiment, the DIFS orAIFS interval duration used by the paged STAs 402, 404, and/or 406 maybe defined in terms of the extended slot time. For example,

AIFS=SIFS+(n*extended slot time)  (5)

DIFS=SIFS+(2*extended slot time)  (6)

In this way, the wireless communications system may be able to reducethe likelihood of collisions, even if the system contains hidden nodes.Hidden nodes are those STAs that are not within range of each other, andso are not aware of the other STAs' existence, yet are in range of theAP. While a hidden node may not sense a PS-POLL request transmitted byone STA, the hidden node will sense a response transmitted by the AP408. By ensuring that the extended slot time is at least as long induration as described herein, even hidden nodes will not decrement theirback-off values until the appropriate time, thereby increasing thelikelihood of avoiding collisions.

As described herein, the extended slot time may be defined as a multipleof a regular slot time, and the DIFS or AIFS interval may be the same asis defined in the IEEE 802.11 standard. As an example, the back-offprocedure used by a paged STA 402, 404, and/or 406 may be implemented byusing a regular back-off procedure. A STA 402, 404, and/or 406 may setthe initial value, i, of the regular back-off counter as follows:

i=K*N _(i)  (7)

where K is as defined in Equation (4) and N_(i) may be a random integerbetween 0 and a duration of a CW or may be deterministically assignedbased on the STA 402, 404, and/or 406 position in the paging messaged asdescribed herein. After the medium has been idle for a DIFS or AIFSinterval of time, the back-off counter is decremented by K units pereach additional consecutive idle interval of a duration equal to anextended slot time. When activity is detected on the medium, theback-off countdown is frozen and is restarted when the medium becomesidle again, as described herein. The STA 402, 404, or 406 transmits apacket on the medium when the back-off reaches zero or any other integerthat represents a lowest value of the counter.

As shown in FIG. 4, AP 408 may complete the transmission of TIM 410 justbefore the beginning of slot time 424 (e.g., an enhanced slot time asdefined herein). Because the channel is idle for the duration of slottime 424, the back-off counter for each of STAs 402, 404, and 406 maydecrease the back-off value. For example, the back-off counter for eachof STAs 402, 404, and 406 may decrement their back-off value by 1, suchthat the back-off value of STA 402 is 0, the back-off value of STA 404is 1, and the back-off value of STA 406 is 2. Since the back-off valuefor STA 402 is 0, STA 402 may transmit a PS-POLL request 412 in the nextslot time, slot time 426. Since STA 402 transmits a PS-POLL request andthe AP 408 transmits a response 414, neither the STA 404 back-offcounter nor the STA 406 back-off counter decrements the back-off value.Note further that a detection of a PS-POLL request or a detection of anAP response may be sufficient to cause the STA 404 back-off counter andthe STA 406 back-off counter to maintain their respective back-offvalues. In this way, even if STA 404 and/or STA 406 is a hidden node,the back-off values will not be decremented.

STAs 404 and 406 maintain the back-off values during slot time 428 aswell because both STAs detect the transmission of response 414 by AP408. During slot time 430, the channel is once again idle. Both the STA404 back-off counter and the STA 406 back-off counter decrement theirrespective back-off values, such that the back-off value for STA 404 isnow 0 and the back-off value for STA 406 is now 1.

In slot time 432, STA 404 transmits a PS-POLL request 416 to the AP 408and the process repeats as described herein until the STA 406 back-offvalue reaches 0 and it transmits a PS-POLL request 420. If a STA 402,404, and/or 406 fails to transmit a PS-POLL 412, 416, and/or 420 duringits allotted time, the subsequent STAs later in the order of STAs maycontinue to decrement their back-off value since the channel willinstead be idle for at least a duration of the extended slot time. Inthis way, delay of the wireless communications system may be reduced orminimized.

In other implementations, not shown, each STA 402, 404, and 406 may bein a sleep mode for a period of time before waking. The sleep time maybe determined based on a position of the STA 402, 404, and 406 in theTIM 410 bitmap sequence and/or an estimation of data sent by the AP 408.After the STA 402, 404, or 406 has waken and the medium has been idlefor a DIFS or AIFS interval of time, the back-off counter is decrementedby K units per each additional consecutive idle interval of a durationequal to an extended slot time. When activity is detected on the medium,the back-off countdown is frozen and is restarted when the mediumbecomes idle again, as described herein. The STA 402, 404, or 406transmits a packet on the medium when the back-off reaches zero or anyother integer that represents a lowest value of the counter. In anotherimplementation, not shown, each STA 402, 404, and 406 may start theback-off counter at a time randomly selected over a given time interval.In still another implementation, not shown, each STA 402, 404, and 406may transmit at a time n*X where n identifies a particular STA and X isa function of the TIM 410 bitmap sequence.

FIG. 5A illustrates a polling request mechanism 500. The polling requestmechanism 500 shown may be used by the AP 104 and the STAs 106 in thewireless communication system 100 of FIG. 1. The polling requestmechanism 500 is similar to the polling request mechanism 400 of FIG. 4.However, in the polling request mechanism 500, an overlapping basicservice set (OBSS) transmission 516 occurs. An OBSS transmission 516 mayoccur if a STA, such as STA 404, identifies with two or more basicservice sets, where each basic service set include an AP and associatedSTAs. The OBSS transmission 516 may originate from an AP other than AP508.

In some implementations, if STA 504 receives an OBSS transmission 516,the STA 504 back-off counter may not decrement the back-off value untilthe OBSS transmission 516 is complete. For example, as illustrated inFIG. 5, OBSS transmission 516 may not be complete until during slot time534 such that the STA 504 back-off counter decrements the back-off valueduring slot time 536, the next slot time in which the channel is idle.However, the STA 506 back-off counter may decrement the back-off valueduring slot time 530 because STA 506 does not detect any transmission onthe channel. For example, STA 506 may determine that the channel is idlefor the duration of slot time 530 because it is not part of the basicservice set for which the OBSS transmission 516 was intended. This mayresult in a situation in which two or more STAs, like STA 504 and STA506, attempt to transmit a PS-POLL request 519 and 520 at or nearly at asame time and cause a collision.

FIG. 5B illustrates a polling request mechanism 550. The polling requestmechanism 550 may reduce the likelihood of a collision occurring asillustrated in FIG. 5A with respect to the polling request mechanism500. The polling request mechanism 550 is similar to the polling requestmechanism 400 of FIG. 4 and the polling request mechanism 500 of FIG.5A. However, in the polling request mechanism 550, the STAs 552 and 556do not transmit a PS-POLL request 562 and 568 at the end of extendedslot time 574 or 586. Rather, at the end of the slot times 574 and 586,the STAs 552 and 556 start an additional short back-off procedure. Theadditional short back-off procedure is based on regular (non-extended)slot times such that a maximum back-off time if the medium was idlewould be shorter than an extended slot time. For example, like STA 504,STA 554 may receive an OBSS transmission 566. While both STA 554 and STA556 may have a back-off value equal to zero during extended slot time586, a collision may be avoided.

In some implementations, the additional back-off counter may beinitialized with a random number or it may be based on a deterministicvalue, like a deterministic back-off value as described herein. Thus,the duration may be based on how the STAs 552, 554, and 556 are orderedin the TIM 560 bitmap sequence. As an example, the back-off procedureused by a paged STA 552, 554, and/or 556 may be implemented by using theregular back-off procedure. A STA 552, 554, or 556 may set the initialvalue, i, of the regular back-off counter as follows:

i=(K*N _(i))+M _(i)  (8)

where K is as defined in Equation (4), N_(i) may be a random integerbetween 0 and a duration of a CW or may be deterministically assignedbased on the STA 402, 404, and/or 406 position in the paging messaged asdescribed herein, and M_(i) may be a random integer between 0 and aduration of a CW′ or may be deterministically determined based on theSTA 402, 404, and/or 406 position in the paging message as describedherein. After the medium has been idle for a DIFS or AIFS interval oftime, the back-off may be decremented by K units per each additionalconsecutive idle interval of a duration equal to an extended slot time.In an embodiment, if the back-off counter value is less than or equal toM_(i), then the back-off counter is decremented by 1 unit per eachadditional consecutive idle interval of a duration equal to a regularslot time. When activity is detected on the medium, the back-offcountdown is frozen and is restarted once the medium becomes idle again,as described herein. The STA 402, 404, or 406 transmits a packet on themedium when the back-off counter reaches zero or any other integer thatrepresents a lowest value of the counter.

In some implementations, the extended slot time may be the sum of thetime it takes for a STA 552, 554, or 556 to transmit a PS-POLL request562, 568, or 572, the short inter-frame space (SIFS) time, the clearchannel assessment (CCA) time, and a maximum contention window time. Inan embodiment, the maximum contention window time may be a maximumnumber of regular slot times that a residual back-off may have (i.e., amaximum value of M_(i)).

Because STA 554 and STA 556 may have different additional back-offperiods (e.g. because both STAs may have different initial residualback-off values), one of STA 554 and STA 556 may transmit a PS-POLLrequest before the other. As shown in FIG. 5B, STA 556 transmits PS-POLLrequest 568 during slot time 588 after the additional back-off periodhas passed, where the additional back-off period begins at the beginningof slot time 588. The additional back-off period for STA 554 also passesduring slot time 588. However, because STA 554 detects the PS-POLLrequest 568 transmitted by STA 556, STA 554 waits at least an additionalslot time before attempting to transmit the PS-POLL request 572 onceagain. Since the channel is busy until after slot time 590, STA 554transmits PS-POLL request 572 after slot time 590 and after itsadditional back-off period has passed.

In other implementations, collisions may still occur. In suchsituations, a STA may transition into a sleep mode and attempt totransmit a request to the AP during the next reserved time interval orafter the current reserved time interval has expired. In this way, whilea delay of the wireless communications system may be increased, energyconsumption may be decreased.

FIG. 6 illustrates a polling request mechanism 600. The polling requestmechanism 600 shown may be used by the AP 104 and the STAs 106 in thewireless communication system 100 of FIG. 1. Unlike the polling requestmechanisms 400, 500, and 550, an extended slot time may not be defined,yet the likelihood of collisions may still be reduced.

As shown in FIG. 6, each STA 602, 604, and 606 waits at least anadaptive enhanced inter-frame space (AEIFS) before attempting totransmit a PS-POLL request 612, 616, or 620 to AP 608. A calculatedAEIFS may prevent each STA 602, 604, and 606 from transmitting a requestuntil the AEIFS duration has expired. Once the AEIFS has passed, the STA602, 604, and/or 606 may transmit the request if the channel is idle. Ifthe channel is not idle, the STA 602, 604, and/or 606 may recalculatethe AEIFS and repeat the above process. The STAs 602, 604, and/or 606may not begin the AEIFS countdown until the channel is idle.

In some implementations, an initial duration of an AEIFS may be based ona position of the respective STA in the STA ordering. The duration ofthe AEIFS for a particular STA may change as other STAs transmit pollingrequests and/or as the AP transmits responses addressed to other STAs.For example, an initial duration of the AEIFS may be calculated by firstsumming a SIFS time, a maximum CW time, and a time it takes a STA 602,604, or 606 to transmit a PS-POLL request 612, 616, or 620 to the AP608. This sum may then be multiplied by the position of the respectiveSTA in the STA ordering as may be defined in the TIM 610 bitmapsequence. The product is then summed with the DIFS time to generate theinitial AEIFS duration. Once a channel is idle, the STA at issue maywait for the initial AEIFS period before determining whether to transmita request.

In some implementations, once a STA detects a PS-POLL request fromanother STA that comes earlier in the STA ordering than the STA at issueor detects a response addressed to another STA that comes earlier in theSTA ordering than the STA at issue, the STA at issue decrements themultiplication factor so as to reduce a duration of the AEIFS. In someembodiments, the decrement of the multiplication factor may also bedetermined by a special indication send by the AP 608 to all of the STAs602, 604, and 606. The indication may be included in the responseaddressed to a STA 602, 604, and/or 606 or may be included in adedicated frame sent for this purpose. For example, if the position ofthe STA at issue in the STA ordering is 3, the initial duration of theAEIFS may be based on the sum as described above multiplied by 3, andthe product summed by the DIFS time. If the STA at issue detects eitherthe PS-POLL request from a STA identified earlier in the TIM 610 bitmapsequence or a response address to a STA identified earlier in the TIM610 bitmap sequence, then the STA at issue may decrement the 3 to avalue of 2 and recalculate the AEIFS. In this way, a STA at issue maywait for the initial AEIFS period before determining whether to transmita request. Once the initial AEIFS period has passed, if the channel isidle, then the STA at issue transmits the request. If the channel is notidle and the STA at issue detects one of the two messages as describedabove, then the STA at issue recalculates the AEIFS. Once the channel isagain idle, the STA at issue then waits the recalculated AEIFS durationbefore determining whether to transmit the request and the processrepeats until the STA at issue is able to transmit the request. In otherembodiments, the STA may wait an additional period of time after theAEIFS duration has passed before attempting to transmit the request.

As shown in FIG. 6, after the AP 608 has completed transmitting the TIM610, STAs 602, 604, and 606 begin to wait for the respective calculatedAEIFS duration. Because STA 602 is first in the order of the three STAs,its AEIFS duration may be shorter than the others. For example, theAEIFS time 624 for STA 602 may be equal to the DIFS time because aposition of the STA 602 in the order of STAs may be represented by a 0.Likewise, the AEIFS time 626 for STA 604 may be calculated with itsposition in the order of STAs represented by 1. The AEIFS time 628 forSTA 606 may be calculated with its position in the order of STAsrepresented by 2. Since STAs 604 and 606 are still waiting when AEIFStime 624 passes, the channel is idle and STA 602 may transmit PS-POLLrequest 612 after its AEIFS time 624 has passed. The PS-POLL request 612causes the AP 608 to generate and transmit a response 614. Because AEIFStime 626 and AEIFS time 628 passes while the response 614 is beingtransmitted, STAs 604 and 606 do not attempt to transmit a request tothe AP 608. If STA 604 or 606 is a hidden node, then the STA may notdetect the PS-POLL request 612 transmitted by STA 602. However, the STAwill detect the response 614 and will thus recalculate its AEIFSduration according to the embodiments described herein. Likewise, if STA604 or 606 is not a hidden node, then the STA may detect both thePS-POLL request 612 and the response 614, and may adjust its AEIFSaccordingly.

Once the AP 608 has completed its transmission of the response 614, STAs604 and 606 may begin to wait for their respective AEIFS times 630 and632. As described herein, once the AEIFS times 630 and 632 pass, therespective STA 604 and 606 checks the channel to determine whether arequest can be transmitted. As illustrated in FIG. 6, STA 604 willdetermine that the channel is idle and transmit PS-POLL request 616,which may result in a response 618. The process described hereincontinues until STA 606 is able to transmit PS-POLL request 620. TheSTAs 602, 604, and 606 may wait an additional period of time, such as acontention window time, before attempting to transmit a request (notshown).

In this way, the use of the AEIFS may allow the wireless communicationssystem to reduce the likelihood of collisions that may occur because ofhidden nodes or other errors. A time that each STA waits beforeattempting to transmit a request may be independent of whether or nothidden nodes exist in the system. By basing a wait time at least partlyon a position of a STA in a TIM bitmap sequence, each STA may wait for aunique time period before attempting to transmit a request. The use ofthe AEIFS may allow the wireless communications system to achievereductions in collisions without creating a longer slot time and withoutincreasing power consumption by the STAs and/or AP.

FIG. 7 is a flowchart of a process 700 for reducing collisions in thewireless communications system of FIG. 1. At block 702, the process 700decrements a value of a counter if a channel of a wirelesscommunications network is idle for at least an extended time slot. In anembodiment, a starting value of the counter is based on a position of anindex corresponding to a wireless communications device in aninformation element, such as a TIM. At block 704, the process 700generates a polling request, such as a PS-POLL request. At block 706,the process 700 transmits the polling request to an access point overthe wireless communications network when the value of the counterreaches a threshold value. After block 706, the process 700 ends.

FIG. 8 is a functional block diagram of an exemplary wireless device 800that may be employed within the wireless communication system 100. Thedevice 800 includes means 802 for decrementing a value of a counter if achannel of a wireless communications network is idle for at least anextended time slot. In an embodiment, means 802 for decrementing a valueof a counter if a channel of a wireless communications network is idlefor at least an extended time slot may be configured to perform one ormore of the functions discussed above with respect to block 702. Thedevice 800 further includes means 804 for generating a polling request.In an embodiment, means 804 for generating a polling request may beconfigured to perform one or more of the functions discussed above withrespect to block 704. The device 800 further includes means 806 fortransmitting the polling request to an access point over the wirelesscommunications network when the value of the counter reaches a thresholdvalue. In an embodiment, means 806 for transmitting the polling requestto an access point over the wireless communications network when thevalue of the counter reaches a threshold value may be configured toperform one or more of the functions discussed above with respect toblock 706.

FIG. 9 is another flowchart of a process 900 for reducing collisions inthe wireless communications system of FIG. 1. At block 902, the process900 generates a polling request, such as a PS-POLL request. At block904, the process 900 determines an adaptive enhanced inter-frame space(AEIFS) each time a wireless communications device detects anothermessage transmitted on a channel of a wireless communications network inwhich the wireless communications device communicates. In an embodiment,an initial duration of the AEIFS is based on a position of the wirelesscommunication device in an information element. At block 906, theprocess 900 transmits the polling request to an access point over thewireless communications network after a time based on a duration of theAEIFS and when the channel of the wireless communications network isopen. After block 906, the process 900 ends.

FIG. 10 is a functional block diagram of an exemplary wireless device1000 that may be employed within the wireless communication system 100.The device 1000 includes means 1002 for generating a polling request. Inan embodiment, means 1002 for generating a polling request may beconfigured to perform one or more of the functions discussed above withrespect to block 902. The device 1000 further includes means 1004 fordetermining an adaptive enhanced inter-frame space (AEIFS) each time awireless communications device detects another message transmitted on achannel of a wireless communications network in which the wirelesscommunications device communicates. In an embodiment, means 1004 fordetermining an AEIFS each time a wireless communications device detectsanother message transmitted on a channel of a wireless communicationsnetwork in which the wireless communications device communicates may beconfigured to perform one or more of the functions discussed above withrespect to block 904. The device 1000 further includes means 1006 fortransmitting the polling request to an access point over the wirelesscommunications network after a time based on a duration of the AEIFS andwhen the channel of the wireless communications network is open. In anembodiment, means 1006 for transmitting the polling request to an accesspoint over the wireless communications network after a time based on aduration of the AEIFS and when the channel of the wirelesscommunications network is open may be configured to perform one or moreof the functions discussed above with respect to block 1006.

As used herein, the term “determining” encompasses a wide variety ofactions. For example, “determining” may include calculating, computing,processing, deriving, investigating, looking up (e.g., looking up in atable, a database or another data structure), ascertaining and the like.Also, “determining” may include receiving (e.g., receiving information),accessing (e.g., accessing data in a memory) and the like. Also,“determining” may include resolving, selecting, choosing, establishingand the like. Further, a “channel width” as used herein may encompass ormay also be referred to as a bandwidth in certain aspects.

As used herein, a phrase referring to “at least one of” a list of itemsrefers to any combination of those items, including single members. Asan example, “at least one of: a, b, or c” is intended to cover: a, b, c,a-b, a-c, b-c, and a-b-c.

The various operations of methods described above may be performed byany suitable means capable of performing the operations, such as varioushardware and/or software component(s), circuits, and/or module(s).Generally, any operations illustrated in the Figures may be performed bycorresponding functional means capable of performing the operations.

The various illustrative logical blocks, modules and circuits describedin connection with the present disclosure may be implemented orperformed with a general purpose processor, a digital signal processor(DSP), an application specific integrated circuit (ASIC), a fieldprogrammable gate array signal (FPGA) or other programmable logic device(PLD), discrete gate or transistor logic, discrete hardware componentsor any combination thereof designed to perform the functions describedherein. A general purpose processor may be a microprocessor, but in thealternative, the processor may be any commercially available processor,controller, microcontroller or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration.

In one or more aspects, the functions described may be implemented inhardware, software, firmware, or any combination thereof. If implementedin software, the functions may be stored on or transmitted over as oneor more instructions or code on a computer-readable medium.Computer-readable media includes both computer storage media andcommunication media including any medium that facilitates transfer of acomputer program from one place to another. A storage media may be anyavailable media that can be accessed by a computer. By way of example,and not limitation, such computer-readable media can comprise RAM, ROM,EEPROM, CD-ROM or other optical disk storage, magnetic disk storage orother magnetic storage devices, or any other medium that can be used tocarry or store desired program code in the form of instructions or datastructures and that can be accessed by a computer. Also, any connectionis properly termed a computer-readable medium. For example, if thesoftware is transmitted from a website, server, or other remote sourceusing a coaxial cable, fiber optic cable, twisted pair, digitalsubscriber line (DSL), or wireless technologies such as infrared, radio,and microwave, then the coaxial cable, fiber optic cable, twisted pair,DSL, or wireless technologies such as infrared, radio, and microwave areincluded in the definition of medium. Disk and disc, as used herein,includes compact disc (CD), laser disc, optical disc, digital versatiledisc (DVD), floppy disk and blu-ray disc where disks usually reproducedata magnetically, while discs reproduce data optically with lasers.Thus, in some aspects computer readable medium may comprisenon-transitory computer readable medium (e.g., tangible media). Inaddition, in some aspects computer readable medium may comprisetransitory computer readable medium (e.g., a signal). Combinations ofthe above should also be included within the scope of computer-readablemedia.

The methods disclosed herein comprise one or more steps or actions forachieving the described method. The method steps and/or actions may beinterchanged with one another without departing from the scope of theclaims. In other words, unless a specific order of steps or actions isspecified, the order and/or use of specific steps and/or actions may bemodified without departing from the scope of the claims.

The functions described may be implemented in hardware, software,firmware or any combination thereof. If implemented in software, thefunctions may be stored as one or more instructions on acomputer-readable medium. A storage media may be any available mediathat can be accessed by a computer. By way of example, and notlimitation, such computer-readable media can comprise RAM, ROM, EEPROM,CD-ROM or other optical disk storage, magnetic disk storage or othermagnetic storage devices, or any other medium that can be used to carryor store desired program code in the form of instructions or datastructures and that can be accessed by a computer. Disk and disc, asused herein, include compact disc (CD), laser disc, optical disc,digital versatile disc (DVD), floppy disk, and Blu-ray® disc where disksusually reproduce data magnetically, while discs reproduce dataoptically with lasers.

Thus, certain aspects may comprise a computer program product forperforming the operations presented herein. For example, such a computerprogram product may comprise a computer readable medium havinginstructions stored (and/or encoded) thereon, the instructions beingexecutable by one or more processors to perform the operations describedherein. For certain aspects, the computer program product may includepackaging material.

Software or instructions may also be transmitted over a transmissionmedium. For example, if the software is transmitted from a website,server, or other remote source using a coaxial cable, fiber optic cable,twisted pair, digital subscriber line (DSL), or wireless technologiessuch as infrared, radio, and microwave, then the coaxial cable, fiberoptic cable, twisted pair, DSL, or wireless technologies such asinfrared, radio, and microwave are included in the definition oftransmission medium.

Further, it should be appreciated that modules and/or other appropriatemeans for performing the methods and techniques described herein can bedownloaded and/or otherwise obtained by a user terminal and/or basestation as applicable. For example, such a device can be coupled to aserver to facilitate the transfer of means for performing the methodsdescribed herein. Alternatively, various methods described herein can beprovided via storage means (e.g., RAM, ROM, a physical storage mediumsuch as a compact disc (CD) or floppy disk, etc.), such that a userterminal and/or base station can obtain the various methods uponcoupling or providing the storage means to the device. Moreover, anyother suitable technique for providing the methods and techniquesdescribed herein to a device can be utilized.

It is to be understood that the claims are not limited to the preciseconfiguration and components illustrated above. Various modifications,changes and variations may be made in the arrangement, operation anddetails of the methods and apparatus described above without departingfrom the scope of the claims.

While the foregoing is directed to aspects of the present disclosure,other and further aspects of the disclosure may be devised withoutdeparting from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

What is claimed is:
 1. A wireless communications device comprising: amemory configured to store a value of a counter; and a processor coupledto the memory, the processor configured to decrement the value of thecounter if a channel of a wireless communications network is idle for atleast an extended slot time, wherein a starting value of the counter isbased on a position of an index corresponding to the wirelesscommunications device in an information element, and configured togenerate a polling request, wherein the polling request is transmittedto an access point over the wireless communications network when thevalue of the counter reaches a threshold value.
 2. The wirelesscommunications device of claim 1, wherein the extended slot time isbased on a duration of a polling request, a duration of a shortinter-frame space (SIFS), and a duration of a clear channel assessment(CCA).
 3. The wireless communications device of claim 1, furthercomprising a receiver electronically coupled to the processor andconfigured to sense messages from the access point, wherein the counteris configured to maintain the value of the counter when the receiversenses a message from the access point.
 4. The wireless communicationsdevice of claim 1, wherein the information element is a trafficindication map (TIM).
 5. The wireless communications device of claim 4,wherein the TIM comprises a bitmap, each bit in the bitmap correspondingto a different wireless communications device in the wirelesscommunications network, and wherein the starting value of the counter isbased on a number of bits corresponding to other wireless communicationsdevices that appear before a bit corresponding to the wirelesscommunication device.
 6. The wireless communications device of claim 1,wherein the access point reserves access to a medium for a group ofwireless communications devices indicated in the information element. 7.The wireless communications device of claim 6, wherein access to themedium is reserved by setting a duration field value of a physical layerdata unit (PPDU) carrying the information element, and wherein settingthe duration field value prompts wireless communications devices notindicated in the information element to set a network allocation vector.8. The wireless communications network of claim 6, wherein wirelesscommunications devices not indicated in the information element are notallowed to access the medium.
 9. The wireless communications device ofclaim 1, wherein the threshold value is zero.
 10. The wirelesscommunications device of claim 1, wherein the extended slot time isbased on a duration of a polling request, a duration of a SIFS, aduration of a CCA, and a duration of a maximum contention window. 11.The wireless communications device of claim 10, wherein the pollingrequest is transmitted to the access point when the value of the counterreaches the threshold value, when the channel is idle, and after a firsttime, the first time based on an arbitration inter-frame spacing (AIFS)and a duration of a residual back-off.
 12. A method for reducingcollisions in a wireless communications network, the method comprising:decrementing a value of a counter if a channel of a wirelesscommunications network is idle for at least an extended slot time,wherein a starting value of the counter is based on a position of anindex corresponding to a wireless communications device in aninformation element; generating a polling request; and transmitting thepolling request to an access point over the wireless communicationsnetwork when the value of the counter reaches a threshold value.
 13. Themethod of claim 12, wherein decrementing a value of a counter comprisesdecrementing the value if the channel is idle for at least a duration ofa polling request, a duration of a short inter-frame space (SIFS), and aduration of a clear channel assessment (CCA).
 14. The method of claim12, further comprising sensing messages from the access point, whereinthe counter is configured to maintain the value of the counter when thereceiver senses a message from the access point.
 15. The method of claim12, further comprising determining the starting value of the counterbased on data in a traffic indication map (TIM).
 16. The method of claim15, further comprising analyzing the TIM, wherein the TIM comprises abitmap, each bit in the bitmap corresponding to a different wirelesscommunications device in the wireless communications network, andwherein the starting value of the counter is based on a number of bitscorresponding to other wireless communications devices that appearbefore a bit corresponding to the wireless communication device.
 17. Themethod of claim 12, wherein the access point reserves access to a mediumfor a group of wireless communications devices indicated in theinformation element.
 18. The method of claim 17, wherein access to themedium is reserved by setting a duration field value of a physical layerdata unit (PPDU) carrying the information element, and wherein settingthe duration field value prompts wireless communications devices notindicated in the information element to set a network allocation vector.19. The method of claim 17, wherein wireless communications devices notindicated in the information element are not allowed to access themedium.
 20. The method of claim 12, wherein the threshold value is zero.21. The method of claim 12, wherein decrementing a value of a countercomprises decrementing the value if the channel is idle for at least aduration of a polling request, a duration of a SIFS, a duration of aCCA, and a duration of a maximum contention window.
 22. The method ofclaim 21, wherein transmitting the polling request comprisestransmitting the polling request to the access point when the value ofthe counter reaches the threshold value, when the channel is idle, andafter a first time, the first time based on an arbitration inter-framespacing (AIFS) and a duration of a residual back-off.
 23. An apparatusconfigured to reduce collisions in a wireless communications network,the apparatus comprising: means for decrementing a value of a counter ifa channel of a wireless communications network is idle for at least anextended slot time, wherein a starting value of the counter is based ona position of an index corresponding to a wireless communications devicein an information element; means for generating a polling request; andmeans for transmitting the polling request to an access point over thewireless communications network when the value of the counter reaches athreshold value.
 24. The apparatus of claim 23, wherein means fordecrementing a value of a counter comprises means for decrementing thevalue if the channel is idle for at least a duration of a pollingrequest, a duration of a short inter-frame space (SIFS), and a durationof a clear channel assessment (CCA).
 25. The apparatus of claim 23,further comprising means for sensing messages from the access point,wherein the counter is configured to maintain the value of the counterwhen the receiver senses a message from the access point.
 26. Theapparatus of claim 23, further comprising means for determining thestarting value of the counter based on data in a traffic indication map(TIM).
 27. The apparatus of claim 26, further comprising means foranalyzing the TIM, wherein the TIM comprises a bitmap, each bit in thebitmap corresponding to a different wireless communications device inthe wireless communications network, and wherein the starting value ofthe counter is based on a number of bits corresponding to other wirelesscommunications devices that appear before a bit corresponding to thewireless communication device.
 28. The apparatus of claim 23, whereinthe access point reserves access to a medium for a group of wirelesscommunications devices indicated in the information element.
 29. Theapparatus of claim 28, wherein access to the medium is reserved bysetting a duration field value of a physical layer data unit (PPDU)carrying the information element, and wherein setting the duration fieldvalue prompts wireless communications devices not indicated in theinformation element to set a network allocation vector.
 30. Theapparatus of claim 28, wherein wireless communications devices notindicated in the information element are not allowed to access themedium.
 31. The apparatus of claim 23, wherein the threshold value iszero.
 32. The apparatus of claim 23, wherein means for decrementing avalue of a counter comprises means for decrementing the value if thechannel is idle for at least a duration of a polling request, a durationof a SIFS, a duration of a CCA, and a duration of a maximum contentionwindow.
 33. The apparatus of claim 32, wherein means for transmittingthe polling request comprises means for transmitting the polling requestto the access point when the value of the counter reaches the thresholdvalue, when the channel is idle, and after a first time, the first timebased on an arbitration inter-frame spacing (AIFS) and a duration of aresidual back-off.
 34. The apparatus of claim 23, wherein the means fordecrementing and the means for generating comprise a processor, andwherein the means for transmitting comprises a transmitter.
 35. Anon-transitory computer-readable medium comprising code that, whenexecuted, causes an apparatus to: decrement a value of a counter if achannel of a wireless communications network is idle for at least anextended slot time, wherein a starting value of the counter is based ona position of an index corresponding to a wireless communications devicein an information element; generate a polling request; and transmit thepolling request to an access point over the wireless communicationsnetwork when the value of the counter reaches a threshold value.
 36. Themedium of claim 35, further comprising code that, when executed, causesthe apparatus to decrement the value if the channel is idle for at leasta duration of a polling request, a duration of a short inter-frame space(SIFS), and a duration of a clear channel assessment (CCA).
 37. Themedium of claim 35, further comprising code that, when executed, causesthe apparatus to sense messages from the access point, wherein thecounter is configured to maintain the value of the counter when thereceiver senses a message from the access point.
 38. The medium of claim35, further comprising code that, when executed, causes the apparatus todetermine the starting value of the counter based on data in a trafficindication map (TIM).
 39. The medium of claim 38, further comprisingcode that, when executed, causes the apparatus to analyze the TIM,wherein the TIM comprises a bitmap, each bit in the bitmap correspondingto a different wireless communications device in the wirelesscommunications network, and wherein the starting value of the counter isbased on a number of bits corresponding to other wireless communicationsdevices that appear before a bit corresponding to the wirelesscommunication device.
 40. The medium of claim 35, wherein the accesspoint reserves access to a second medium for a group of wirelesscommunications devices indicated in the information element.
 41. Themedium of claim 40, wherein access to the second medium is reserved bysetting a duration field value of a physical layer data unit (PPDU)carrying the information element, and wherein setting the duration fieldvalue prompts wireless communications devices not indicated in theinformation element to set a network allocation vector.
 42. The mediumof claim 40, wherein wireless communications devices not indicated inthe information element are not allowed to access the second medium. 43.The medium of claim 35, wherein the threshold value is zero.
 44. Themedium of claim 35, further comprising code that, when executed, causesthe apparatus to decrement the value if the channel is idle for at leasta duration of a polling request, a duration of a SIFS, a duration of aCCA, and a duration of a maximum contention window.
 45. The medium ofclaim 44, further comprising code that, when executed, causes theapparatus to transmit the polling request to the access point when thevalue of the counter reaches the threshold value, when the channel isidle, and after a first time, the first time based on an arbitrationinter-frame spacing (AIFS) and a duration of a residual back-off.
 46. Awireless communications device comprising: a receiver configured todetect messages transmitted on a channel of a wireless communicationsnetwork; and a processor coupled to the receiver, the processorconfigured to generate a polling request and configured to determine anadaptive enhanced inter-frame space (AEIFS) each time the receiverdetects another message transmitted on the channel of the wirelesscommunications network in which the wireless communications devicecommunicates, wherein an initial duration of the AEIFS is based on aposition of the wireless communication device in an information element,and wherein the polling request is transmitted to an access point overthe wireless communications network after a time based on a duration ofthe AEIFS and when the channel of the wireless communications network isopen.
 47. The wireless communications device of claim 46, wherein theinformation element is a traffic indication map (TIM).
 48. The wirelesscommunications device of claim 47, wherein the TIM comprises a bitmap,each bit in the bitmap corresponding to a different wirelesscommunications device in the wireless communications network, andwherein the initial duration of the AEIFS is based on a number of bitscorresponding to other wireless communications devices that appearbefore a bit corresponding to the wireless communication device.
 49. Thewireless communications device of claim 48, wherein the duration of theAEIFS is based on a duration of a distributed coordinate functioninter-frame space (DIFS), a duration of a short inter-frame space(SIFS), a duration of a maximum contention window, a transmit time of apolling request, and a number of messages transmitted by the accesspoint addressed to other wireless communications devices that correspondto a bit that appears before the bit corresponding to the wirelesscommunications device.
 50. The wireless communications device of claim49, wherein the duration of the AEIFS decreases as the number ofmessages transmitted by the access point addressed to other wirelesscommunications devices that correspond to a bit that appears before thebit corresponding to the wireless communications device increases. 51.The wireless communications device of claim 50, further comprising atransmitter configured to transmit the polling request when the accesspoint has addressed a message to each other wireless communicationsdevice that corresponds to a bit that appears before the bitcorresponding to the wireless communications device.
 52. The wirelesscommunications device of claim 46, further comprising a receiverelectronically coupled to the processor and configured to detectmessages on the channel.
 53. A method for reducing collisions in awireless communications network, the method comprising: generating apolling request; determining an adaptive enhanced inter-frame space(AEIFS) each time a wireless communications device detects anothermessage transmitted on a channel of a wireless communications network inwhich the wireless communications device communicates, wherein aninitial duration of the AEIFS is based on a position of the wirelesscommunication device in an information element; and transmitting thepolling request to an access point over the wireless communicationsnetwork after a time based on a duration of the AEIFS and when thechannel of the wireless communications network is open.
 54. The methodof claim 53, further comprising determining an initial duration of theAEIFS based on data in a traffic indication map (TIM).
 55. The method ofclaim 54, further comprising analyzing the TIM, wherein the TIMcomprises a bitmap, each bit in the bitmap corresponding to a differentwireless communications device in the wireless communications network,and wherein the initial duration of the AEIFS is based on a number ofbits corresponding to other wireless communications devices that appearbefore a bit corresponding to the wireless communication device.
 56. Themethod of claim 55, further comprising determining a duration of theAEIFS based on a duration of a distributed coordinate functioninter-frame space (DIFS), a duration of a short inter-frame space(SIFS), a duration of a maximum contention window, a transmit time of apolling request, and a number of messages transmitted by the accesspoint addressed to other wireless communications devices that correspondto a bit that appears before the bit corresponding to the wirelesscommunications device.
 57. The method of claim 56, further comprisingdecreasing the duration of the AEIFS as the number of messagestransmitted by the access point addressed to other wirelesscommunications devices that correspond to a bit that appears before thebit corresponding to the wireless communications device increases. 58.The method of claim 57, wherein transmitting the polling requestcomprises transmitting the polling request when the access point hasaddressed a message to each other wireless communications device thatcorresponds to a bit that appears before the bit corresponding to thewireless communications device.
 59. An apparatus configured to reducecollisions in a wireless communications network, the apparatuscomprising: means for generating a polling request; means fordetermining an adaptive enhanced inter-frame space (AEIFS) each time awireless communications device detects another message transmitted on achannel of a wireless communications network in which the wirelesscommunications device communicates, wherein an initial duration of theAEIFS is based on a position of the wireless communication device in aninformation element; and means for transmitting the polling request toan access point over the wireless communications network after a timebased on a duration of the AEIFS and when the channel of the wirelesscommunications network is open.
 60. The apparatus of claim 59, furthercomprising means for determining an initial duration of the AEIFS basedon data in a traffic indication map (TIM).
 61. The apparatus of claim60, further comprising means for analyzing the TIM, wherein the TIMcomprises a bitmap, each bit in the bitmap corresponding to a differentwireless communications device in the wireless communications network,and wherein the initial duration of the AEIFS is based on a number ofbits corresponding to other wireless communications devices that appearbefore a bit corresponding to the wireless communication device.
 62. Theapparatus of claim 61, further comprising means for determining aduration of the AEIFS based on a duration of a distributed coordinatefunction inter-frame space (DIFS), a duration of a short inter-framespace (SIFS), a duration of a maximum contention window, a transmit timeof a polling request, and a number of messages transmitted by the accesspoint addressed to other wireless communications devices that correspondto a bit that appears before the bit corresponding to the wirelesscommunications device.
 63. The apparatus of claim 62, further comprisingmeans for decreasing the duration of the AEIFS as the number of messagestransmitted by the access point addressed to other wirelesscommunications devices that correspond to a bit that appears before thebit corresponding to the wireless communications device increases. 64.The apparatus of claim 63, wherein means for transmitting the pollingrequest comprises means for transmitting the polling request when theaccess point has addressed a message to each other wirelesscommunications device that corresponds to a bit that appears before thebit corresponding to the wireless communications device.
 65. Theapparatus of claim 59, wherein the means for generating and the meansfor determining comprise a processor, and wherein the means fortransmitting comprise a transmitter.
 66. A non-transitorycomputer-readable medium comprising code that, when executed, causes anapparatus to: generate a polling request; determine an adaptive enhancedinter-frame space (AEIFS) each time a wireless communications devicedetects another message transmitted on a channel of a wirelesscommunications network in which the wireless communications devicecommunicates, wherein an initial duration of the AEIFS is based on aposition of the wireless communication device in an information element;and transmit the polling request to an access point over the wirelesscommunications network after a time based on a duration of the AEIFS andwhen the channel of the wireless communications network is open.
 67. Themedium of claim 66, further comprising code that, when executed, causesthe apparatus to determine an initial duration of the AEIFS based ondata in a traffic indication map (TIM).
 68. The medium of claim 67,further comprising code that, when executed, causes the apparatus toanalyze the TIM, wherein the TIM comprises a bitmap, each bit in thebitmap corresponding to a different wireless communications device inthe wireless communications network, and wherein the initial duration ofthe AEIFS is based on a number of bits corresponding to other wirelesscommunications devices that appear before a bit corresponding to thewireless communication device.
 69. The medium of claim 68, furthercomprising code that, when executed, causes the apparatus to determine aduration of the AEIFS based on a duration of a distributed coordinatefunction inter-frame space (DIFS), a duration of a short inter-framespace (SIFS), a duration of a maximum contention window, a transmit timeof a polling request, and a number of messages transmitted by the accesspoint addressed to other wireless communications devices that correspondto a bit that appears before the bit corresponding to the wirelesscommunications device.
 70. The medium of claim 69, further comprisingcode that, when executed, causes the apparatus to decrease the durationof the AEIFS as the number of messages transmitted by the access pointaddressed to other wireless communications devices that correspond to abit that appears before the bit corresponding to the wirelesscommunications device increases.
 71. The medium of claim 70, furthercomprising code that, when executed, causes the apparatus to transmitthe polling request comprises means for transmitting the polling requestwhen the access point has addressed a message to each other wirelesscommunications device that corresponds to a bit that appears before thebit corresponding to the wireless communications device.